Add pr-rebuild configuration.
Removes the old script, adds documentation stub
Merge pull request #20 from skyluc/new-zinc-build/clean-up

Removes the old script, adds documentation stub
Removes USE_PROVIDED_MAVEN_TGZ flag, and all related code

This support is being removed from the Scala PR validation build.
Updates support for building from custom Scala

Reworks a bit the flags
Adds support for versions.properties file
Adds ability to force the cache functions
Renames the cache functions
Adds a basic configuration to build from custom Scala
Adds some documentation about release, release-dryrun, scala-local-build and nightly
Forces Scala branch to build for pr validation
Merge pull request #21 from skyluc/new-zinc-build/scala-to-scala-ide-build

Updates Scala to Scala ide build
Fixes support for scala-pr-validator

Uses a provided versions.properties file
Keeps defind MAVEN_ARGS
Adds extra param for zinc dbuild
Added some doc.
Merge pull request #22 from skyluc/new-zinc-build/scala-pr-validator

Fixes support for scala-pr-validator
Fixes check for uploading plugins
config for 4.0.x releases on 2.11.x
Adds git fetch for tags

The simple `git fetch` doesn't import the tags from the remote,
the additionnal `git fetch --tag` is needed.
Merge pull request #23 from skyluc/issue/not-refreshing-tags

Adds git fetch for tags